This invention relates generally to computers, and more particularly to an apparatus that facilitates the installation or removal of a removable cover component of a computer enclosure.
As it is known in the art, computer systems typically have many components, such as disk storage or printers, which are normally encased within a metal enclosure, having detachable or removable covers. Many computer systems and peripherals require these removable covers to access internal components for servicing or upgrading purposes. These covers, which are usually part of the "outer skin" of the computer, however, are not shielded in and of themselves. The encased electronic components are capable of conducting electromagnetic signals inside the package, and electromagnetic signals can radiate and leak out from the detachable covers. Such electromagnetic emissions can significantly impact the performance of other proximate electronic components that are not within the enclosure, as well as protecting components within the enclosure from the emissions of the other proximate electronic components. Since the trend in computer systems is towards faster and higher frequency devices, and hence higher magnitudes of emissions, this degradation in performance is further magnified.
Thus, shielding of the critical inner components with a sealed enclosure of highly conductive material is necessary. One common response to this necessity in industry with these types of removable covers requires compliant spring fingers around the cover's perimeters to make grounding contact with the computer enclosure in order to "seal" in the electromagnetic emissions within the enclosure when operating. The spring finger is made of electrically conductive material and through the use of fingers around the edges of the cover or base enclosure, grounding contact is achieved via the fingers when the cover is installed. Typically, with modern computers, numerous contact points along the perimeter of the cover are required to accomplish this task.
Several basic problems arise in conventional computer systems, when providing removable covers with these spring fingers on contact points. Generally, the use of many spring fingers or strips of spring fingers require hardware or tools, such as a series of screws along the perimeter of the cover, to install. This type of installation, though arguably reliable, can be very impractical, costly and further, it can be very time consuming for the product operator or customer during removal/installation of the covers.
Another method of installation utilizing adhesive to mount the spring fingers leads to a familiar problem of unreliable long-term installation. Here, there is a tendency for the adhesive to dry out over time and lose its holding power. This predicament is especially magnified when the adhesive is used on covers which are frequently pulled on and off over a span of many years.
A still further potential deterrent with strips of spring fingers, is that they are easily snagged, susceptible to damage and deformation, and can be torn off or permanently distorted if the product assembler or customer is required to frequently handle or grip the edges of the cover where the fingers are mounted. Also, because strips are extremely thin and flexible, acute edges may produce risky conditions.
Another problem arises when the orientation at which the spring finger slides best over its mating contact surface is not consistent with the direction for cover installation or removal.
Additionally, in many cases, the spring fingers do not provide maximum compliance to provide a good grounding contact, while still providing for a cover that is easily installable or removable under a broad range of conditions. Notably, too much spring force will increase friction and make the cover difficult to remove or install.
One common solution to the above-mentioned types of problems, is to provide clip-on spring fingers on compliant strips This arrangement, however, is still subject to snagging when installing or removing, since the finger orientation is typically at a 90 degree axis to the sliding direction. Further, even if the ends of each spring finger were buried under the thickness of the cover flange, the protruding edges are still subject to snagging by the user or on imperfections along the mating contact surfaces of the computer enclosure.
Another solution for providing easy installation and non-snag features, is what is known in the prior art as the "wavy finger" strip. Because each finger is dependent on the adjacent finger for its deflection, this design has little compliance, or in other words, not all spring fingers are guaranteed to make contact with the mating surface of the computer enclosure. For instance, when a particular finger is deflected in a downward direction, the adjacent fingers may be deflecting upwards.
A still further solution to contact problems in the prior art is to provide individual spring fingers which clip into place and do not snag when installing or removing. However, being individual springs, installation is very time consuming and expensive. Also, with this type of design, the compliance is somewhat sensitive since the deflection force is similar to that of a simple beam with free ends, whereby the spring material must slide across the metal edges of the cover cutouts in order to deflect. Thus, this type of design produces a relatively stiff spring.